Posted November 2nd, 2022 at 8:04 pm by Dan Musick
Limit switches are used to keep the garage door opener from trying to open a garage door that is already open, or trying to close a door that is already closed. Throughout the history of garage doors, engineers have come up with a wide variety of limit switch designs. We have listed a few of them here.
See this article for more information about limit switches and how to adjust them.
The most common limit switch comes in most of the Sears, Chamberlain and Liftmaster openers made since the early nineties.
Another common type of limit switch found on commercial and industrial operators uses a limit shaft with two plastic nuts, as shown on this LiftMaster operator.
PowerMaster operators use plastic nuts with a design similar to the LiftMaster limit assemblies.
The older Edko operators used wooden nuts that slid between the open and closed switches.
Link operators used plastic nuts sliding along the limit shaft.
McKeon operators use a similar system with round plastic nuts. A steel plate prevents the nuts from turning on the shaft as the shaft turns.
The older Crane operators used limit assemblies with two nuts.
Other types of limit switches
Allister, Allstar, and MVP openers normally used chain dogs to stop the door as it opens and closes.
In the image below, you can see where the limit dog has moved an arm. The arm then activated the switch to stop the door travel. The limit dog can be adjusted by loosening the screw that secures the dog to the chain.
Historically, Genie has used limit switches mounted to the track.
The older Scientific operators also used track-mounted switches to stop the door as it opened and closed.
The older Vemco operators used a small tube that ran the full length of the operator rail.
You can also install auxiliary limit switches along with operator counters to count the number of times your garage door opens and closes. See our post explaining how to install operator counters for more information.